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VCF help?

VCF help?

2004-07-05 by charlesosthelder

Hey all!

My Steiner-Stone VCF is together and includes the John Lofflink mods
for MOTM. I'm not using a direct CV input, and maybe this is what's
causing my dillema - the positive-going EG's don't work with the
filter. The positive half of an LFO waveform works fine. The
inverted EG output of the MOTM-800 works in a strange fashion and
not as expected. Could it be that simply turning the CV control all
the way up is not enough for the EG outs? I thought I could get
away with one less input jack.

Aside from CV woes, the filter sounds great! This will see a lot of
use when the

Re: VCF help? - not needed!

2004-07-05 by charlesosthelder

Once again, reading is FUNdamental.

Sorry for wasting the bandwidth. Ken, John et al., the filter is
SWEET!

Chub
Show quoted textHide quoted text

--- In cgs_synth@yahoogroups.com, "charlesosthelder"
<osthelder@n...> wrote:
> Hey all!
>
> My Steiner-Stone VCF is together and includes the John Lofflink
mods
> for MOTM. I'm not using a direct CV input, and maybe this is
what's
> causing my dillema - the positive-going EG's don't work with the
> filter. The positive half of an LFO waveform works fine. The
> inverted EG output of the MOTM-800 works in a strange fashion and
> not as expected. Could it be that simply turning the CV control
all
> the way up is not enough for the EG outs? I thought I could get
> away with one less input jack.
>
> Aside from CV woes, the filter sounds great! This will see a lot
of
> use when the

Re: VCF help?

2004-07-05 by sasami@hotkey.net.au

Try reducing the resistor in series with the CV control to give you more
range. ALso consider taking the CCW end of the pot to -VE instead of 0V just
to see what happens.

That postitive envelopes don't work is a puzzle though.Must be some sort of
offset involved.

Ken
Show quoted textHide quoted text
>Hey all!
>
>My Steiner-Stone VCF is together and includes the John Lofflink mods
>for MOTM. I'm not using a direct CV input, and maybe this is what's
>causing my dillema - the positive-going EG's don't work with the
>filter. The positive half of an LFO waveform works fine. The
>inverted EG output of the MOTM-800 works in a strange fashion and
>not as expected. Could it be that simply turning the CV control all
>the way up is not enough for the EG outs? I thought I could get
>away with one less input jack.
>
>Aside from CV woes, the filter sounds great! This will see a lot of
>use when the
>
>
>
>
>See the following URLS for the CGS Modular Synth home page:
>Main: http://www.cgs.synth.net/
>Secondary: http://otherunicorn.0catch.com/synth/
>Yahoo! Groups Links
>
>
>
>
>
>
_______________________________________________________________________
Ken Stone sasami@... or sasami@...
Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>

Re: VCF help?

2004-07-05 by John Loffink

Note the comment "positive going EGs don't work" but "positive half of LFO
waveform works fine." Are you sure your EG is functioning correctly?

John Loffink
The Microtonal Synthesis Web Site
http://www.microtonal-synthesis.com
The Wavemakers Synthesizer Web Site
http://www.wavemakers-synth.com
Show quoted textHide quoted text
> -----Original Message-----
> From: sasami@... [mailto:sasami@...]
> Sent: Monday, July 05, 2004 6:44 PM
> To: cgs_synth@yahoogroups.com
> Subject: Re: [cgs_synth] VCF help?
>
> Try reducing the resistor in series with the CV control to give you more
> range. ALso consider taking the CCW end of the pot to -VE instead of 0V
> just
> to see what happens.
>
> That postitive envelopes don't work is a puzzle though.Must be some sort
> of
> offset involved.
>
> Ken
>
> >Hey all!
> >
> >My Steiner-Stone VCF is together and includes the John Lofflink mods
> >for MOTM. I'm not using a direct CV input, and maybe this is what's
> >causing my dillema - the positive-going EG's don't work with the
> >filter. The positive half of an LFO waveform works fine. The
> >inverted EG output of the MOTM-800 works in a strange fashion and
> >not as expected. Could it be that simply turning the CV control all
> >the way up is not enough for the EG outs? I thought I could get
> >away with one less input jack.
> >
> >Aside from CV woes, the filter sounds great! This will see a lot of
> >use when the
> >
> >
> >
> >
> >See the following URLS for the CGS Modular Synth home page:
> >Main: http://www.cgs.synth.net/
> >Secondary: http://otherunicorn.0catch.com/synth/
> >Yahoo! Groups Links
> >
> >
> >
> >
> >
> >
> _______________________________________________________________________
> Ken Stone sasami@... or sasami@...
> Modular Synth PCBs for sale <http://www.blaze.net.au/~sasami/synth/>
> Australian Miniature Horses & Ponies <http://www.blaze.net.au/~sasami/>
>
>
>
>
> See the following URLS for the CGS Modular Synth home page:
> Main: http://www.cgs.synth.net/
> Secondary: http://otherunicorn.0catch.com/synth/
> Yahoo! Groups Links
>
>
>
>

Re: VCF help?

2004-07-06 by charlesosthelder

Thanks guys. All good suggestions, but the REAL problem is following
directions!

I omitted the extra series resistance that John recommends in his
MOTM build-up. Once I changed the 220K on the wiper of the freq pot
to a 470K, all was well. It may help others to note that I matched
the 2n2222's in the circuit (all have hfe 0f 148. These are old
Motorola metal cans) and dug through my 2n3906's until I found one
with a low hfe - about 155 - and low noise.

In fact all is VERY well! This is a neat filter. Right now I've got
a patch using two VCO's, the BP and LP inputs of the filter with the
freq knob below the lowest fundamental of the VCO's. The resonance
is fairly low and the EG is set for a quick attack, medium decay and
minimal sustain and resonance. The VCO patched to the BP input has a
slight vibrato from the FM input. It sounds like an alien bell
tolling. Cool stuff!

Thanks again!

Chub

Chub

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